package main

import (
	"context"
	"log"
	"net/http"
	"os"
	"os/signal"
	"sync"
	"syscall"
	"time"
)

var (
	shutdownMu   sync.Mutex
	shutdownFns  []func()
	hooksOnce    sync.Once
	bgHandlerOnce sync.Once
)

// registerShutdown runs fn on SIGINT/SIGTERM (LIFO order).
func registerShutdown(fn func()) {
	shutdownMu.Lock()
	shutdownFns = append(shutdownFns, fn)
	shutdownMu.Unlock()
}

func runShutdownHooks() {
	hooksOnce.Do(func() {
		shutdownMu.Lock()
		fns := shutdownFns
		shutdownMu.Unlock()
		for i := len(fns) - 1; i >= 0; i-- {
			fns[i]()
		}
	})
}

// enableShutdownOnInterrupt listens for SIGINT/SIGTERM in the background and exits
// after running shutdown hooks. Use for one-shot CLI commands (OTA, etc.).
func enableShutdownOnInterrupt() {
	bgHandlerOnce.Do(func() {
		ch := make(chan os.Signal, 1)
		signal.Notify(ch, os.Interrupt, syscall.SIGTERM)
		go func() {
			sig := <-ch
			signal.Stop(ch)
			log.Printf("received %v, shutting down…", sig)
			runShutdownHooks()
			os.Exit(0)
		}()
	})
}

// waitForShutdown blocks until SIGINT/SIGTERM, runs hooks, and returns.
// Use for long-running servers (serve/dashboard).
func waitForShutdown() {
	ch := make(chan os.Signal, 1)
	signal.Notify(ch, os.Interrupt, syscall.SIGTERM)
	sig := <-ch
	signal.Stop(ch)
	log.Printf("received %v, shutting down…", sig)
	runShutdownHooks()
}

func shutdownHTTPServer(srv *http.Server) {
	if srv == nil {
		return
	}
	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()
	if err := srv.Shutdown(ctx); err != nil {
		log.Printf("HTTP shutdown: %v", err)
	}
}